1000 watt pole light bursting lens

tdexxx

Member
I have worked on pole lights before but never before yesterday have seen a pole light fixture lens burst after replacing a lamp. The fixtures in question are about 30 feet up, 1000 watt Metal Halide and the lamps are vertically mounted BT37s. The fixture is the kind that you access by unscrewing four philips head screws holding down the square lit and lifting the lid off. This is a pretty common type of fixture at big box stores. The horizontally square lens fits into the bottom of the fixture and is shaped into a vertically-distended hemisphere.

A few minutes after installing a new lamp into a fixture, turning it on to make sure it was burning normally, and then driving off to the next outage, the fixtuire's lens burst showering cars below with shards of glass about the size and shape of large french fries. The lens didn't fall out in a one or several large pieces and break on the ground, it burst in place with a loud sound, (I was told: I was a couple of minutes away from it when it happened). It scared the Kee-rap out of me because I'm always worried something I work on could fall and hurt someone, as this falling glass could have but luckily did not. The lamp continued to burn, but without a lens, and it seemed to be burning normally so I have no reason to suspect that some malfunction of the lamp caused the lens to break.

Anyway, I can't think of anything I may have done wrong on this job to make that lens burst. The fixture calls for a bt37, and that's what I installed. The only think I can think to suspect is that our hot, very muggy weather allowed moisture to infiltrate the glass of the lens, and the lens burst as the result of the lamp's sudden heat. But, I have worked on plenty of parking lot lights before and nothing like this has ever happened to me. The fixtures are old, I don't know if that matters.

Has anyone here experienced this, or can you suggest to me something I may have done to cause the lens to break?

Tom
 

mirawho

Senior Member
In the early 70's I did a lot of neon and lighting, including parking lot and stadium luminaires. I don't think I ever remember one bursting after I replaced a lamp as the glass is tempered. The only thing I could think this might be a combination of minute fractures or imperfections in the lens. I can't imagine, from your description, that there was anything you could have done different that would have prevented this. There had to be some kind of glass fracture to make this happen. The lens is rated for the lamp. Recently we had gone through a bunch of lenses on our 4000W HMI pars on a show. We had found out that the manufacturer had switched suppliers for the lens kits and the glass was thin at some points creating fractures in the lens, causing them to burst while we were on a hot set.
 

fmtjfw

Senior Member
I have worked on pole lights before but never before yesterday have seen a pole light fixture lens burst after replacing a lamp. The fixtures in question are about 30 feet up, 1000 watt Metal Halide and the lamps are vertically mounted BT37s. The fixture is the kind that you access by unscrewing four philips head screws holding down the square lit and lifting the lid off. This is a pretty common type of fixture at big box stores. The horizontally square lens fits into the bottom of the fixture and is shaped into a vertically-distended hemisphere.

A few minutes after installing a new lamp into a fixture, turning it on to make sure it was burning normally, and then driving off to the next outage, the fixtuire's lens burst showering cars below with shards of glass about the size and shape of large french fries. The lens didn't fall out in a one or several large pieces and break on the ground, it burst in place with a loud sound, (I was told: I was a couple of minutes away from it when it happened). It scared the Kee-rap out of me because I'm always worried something I work on could fall and hurt someone, as this falling glass could have but luckily did not. The lamp continued to burn, but without a lens, and it seemed to be burning normally so I have no reason to suspect that some malfunction of the lamp caused the lens to break.

Anyway, I can't think of anything I may have done wrong on this job to make that lens burst. The fixture calls for a bt37, and that's what I installed. The only think I can think to suspect is that our hot, very muggy weather allowed moisture to infiltrate the glass of the lens, and the lens burst as the result of the lamp's sudden heat. But, I have worked on plenty of parking lot lights before and nothing like this has ever happened to me. The fixtures are old, I don't know if that matters.

Has anyone here experienced this, or can you suggest to me something I may have done to cause the lens to break?

Tom
When you put the cover back on, was it "level" or did it bind? If the glass was stressed by something causing uneven pressure on it?
 

tdexxx

Member
When you put the cover back on, was it "level" or did it bind? If the glass was stressed by something causing uneven pressure on it?
Well, I say there was no bind because the lens in this fixture is build into the "shoebox", and so there's no swinging "trap door" lens frame, and so no way to create stress in the lens other than by deforming the entire body of the fixture, which is pretty sturdy. So, it's hard for me to see how the lens could have been twisted, stretched, or bent at all.

Tom
 
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mgookin

Senior Member
Well it wasn't tempered glass if it broke into fragments the size of French fries.

Maybe a call to the manuf to see if they know of this happening before.
 
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